x\n overwhelming part of the seaweeds known have been found in 

 the American sector of West Antarctica on the Pacific side. Little is 

 known about the flora of East Antarctica, the most important contribution 

 having been made by " Banzare " expeditions. The author is at present 

 studying this collection, which adds much to our knowledge and contains 

 some undescribed species. 



At present we know 12 ChlorophycecB, about 65 RhodphycecB, and 

 18 or 19 PhcBophycece from the Antarctic. All groups contain some 

 -endemic species, but the bulk is formed b}- subantarctic forms, of which 

 some are Circumpolar. A remarkable degree of endemism is shown only 

 by the Phceophycece , with 5 endemic genera, some of which have no 

 ■close relatives. The arctic flora gives exactly the same impression, 

 but is much richer. This is in accordance with the distribution of land 

 and sea in the north, where the transition from the Subarctic to the 

 Arctic zone is quite gradual. The Antarctic and subantarctic zones are 

 separated by wide expanses of water, probably crossed by dispersal units 

 only on rare occasions and hardly ever in the direction north-south, or 

 vice versa, because of the west wind drift. Another reason for the poverty 

 of the Antarctic hes in its history since the beginning of the Ice Age. Life 

 conditions are very severe, as they are now, suitable localities for marine 

 algas in the intertidal region being of very limited extent because of both 

 the extension of the inland and shelf ice and of the destructive action of 

 the sea ice in motion. During the maximum glaciation conditions must 

 have been much worse, the refuges were few, and only the hardier species 

 survived. During the post-Glacial a gradual reimmigration took place. 

 Even South Georgia was almost entirely ice-covered and its marine flora 

 must have suffered great losses. Nevertheless, it shows a remarkable 

 number of outstanding endemic types. The glaciation did not have the 

 same destructive influence in the Arctic, where the algse could retreat 

 south along the coasts of both the Altantic and the Pacific. 



It is very difficult to get a firm hold on the pre-Glacial history of the 

 Antarctic algae. They belong to an extreme cold-water flora which, as far 

 as we are able to judge, cannot exist under Temperate conditions. 

 Marine algae are sensitive in this respect ; they are, all over the globe, 

 distributed in distinct zones of temperature. If we go back to the 

 Tertiary, we soon get to a point where there was no cold water at all. 

 Of course, already during Eocene — and before — climatic zones existed, 

 and they became more pronounced in the Oligocene and Miocene, buc the 

 land flora in the Polar regions was more or less subtropical, both south 

 and north, and the seas must have been warm. A source of cold came 

 into existence with the formation of mountain ranges, in the south, the 

 Antarctandes. Here Temperate-montane and Alpine land floras 

 developed. Snow and ice accumulated on the mountains, which were 

 higher than now, glaciers descended into the valleys, and eventually 

 reached sea-level, inaugurating the era when a marine flora, adapted to 

 cold water, was born, the ancestors of the present-day flora, just as the 

 Sub-tropical penguins, found as fossils in old Tertiary strata on the Palmer 

 Peninsula, are the ancestors of the living cold-water penguins. Thus 

 the truly Antarctic marine bios is comparatively recent. 



Another factor to be taken into account is the supposed land 

 connections between the Antarctic and subantarctic. They affected the 

 currents profoundly, and circumpolar dispersal was impossible. We 

 face a very complicated problem here, and it will require a lot of thinking 

 to understand the influence of such land connections on the evolution 



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